Rigid connections between members in a mechanical system can be a path of vibrational propagation between members. One arrangement in which this can occur is in a refrigeration system chiller where a compressor is mounted on a heat exchanger by a rigid connection through which fluid is transferred.
Screw compressors, especially high speed geared compressors, generate high levels of structure borne energy in a frequency range where components of the systems in which they are typically applied are very responsive. This often leads to unacceptably high radiated sound levels from both the compressors and the rigidly attached system components. The problem is particularly acute with compressors designed to be directly mounted on a heat exchanger shell such that the compressor is fully supported by a flange extending directly from the shell. This is because this joint tends to transmit energy very efficiently from the compressor to the heat exchanger shell. Reducing this transmission by conventional means such as elastomeric or helical springs is very difficult due to the conflicting requirements placed on the joint. Specifically, the joint must hermetically contain the refrigerant, withstand the operating pressure in the system, and be structurally robust, especially if the joint represents the sole support for the compressor. Additionally, space requirements are often very restrictive since minimizing package size is critical.
Several designs have been formulated to address the radiation of structurebome noise. They involve structurally decoupling the compressor from the heat exchanger. When transient events occur, however, the flexibility of the isolator may allow too much compressor motion. Additionally, during pressure testing in the factory, stress levels in the isolator may induce yielding, which would have a potential negative impact on performance and reliability.